Three default taxonomies are used here, lingua, tags, and categories.
By convention, taxonomies that are typically single-valued use the singular
(for example lingua because a document can be written in only one
language), taxonomies that can have multiple values usually use the
plural form.

Taxonomies allow you to partition or divide your web site into groups of
related documents. For example, you can identify all English documents
with the condition lingua="en".

All English documents.

Likewise, you can identify all documents that are tagged with Qgoda.

All documents tagged with "Qgoda".

By combining taxonomies you can define arbitrary subsets of a site's documents.
You can for example identify all English documents tagged with Qgoda and
Plug-Ins by AND'-ing the two above conditions.